What are the others known solar systems ?
Technically, there is only one Solar system, as this is derived from Sol, our sun's name. So these are the known stellar systems.
These planets look like stars!
No, they don't - most look like Jupiter. And in any case, we can't see them directly anyway.
From the caption:
Wow, I didn't realize that was possible....
Anyway, this article implies that that is the only such photo yet taken and it is only possible because the planet is large and orbiting a brown dwarf at a large distance and both are imaged in infrared. A very unusual case. http://www.eso.org/public/news/eso0511/
In the time since then, a handful of exoplanets have been directly imaged, including in the visible.
Of course, seeing the shadow is even simpler.
There are a few other photos of other planets, but they are definitely still the exception rather than the rule. The http://www.physorg.com/news185795684.html" [Broken] was captured with visible light! As with so many things in astronomy, it's only a matter of time. We're taking the most amazing pictures ever, and I can't wait to see how the technology improves.
As i recall 3 planets - out of which one was actually a brown dwarf - has been observed directly so far.
But we will be able to see them very soon; New techniques to substract the stellar glare from exoplanets observations, promises to make it possible for todays earth based telescopes to see them
See the articles at http://www.spacedog.eu/astronomy/exoplanets/ [Broken]
And with the James Weeb 8m spacetelescope in 2015, the ESO 45m OWL telescope and several others, we will soon also have far more raw resolution power to work with.
But to answer the question:
The Gliese 581-system is a small dwarf-star surrounded by at least 4 planets, out of which 2 are gas-giants and one is an icy planet. But the fourth planet - Gliese581C is a rocky planet5x heavier than Earth, which is covered with a deep ocean!
How do we know this?
Fairly "simple": It has been discovered through the transit method, which allow the astronomers to measure its diameter, based on how much light it's shadow "steals" from the mother-star. Based on the start wobble, it's mass camn be measured.
This has lead to tyhe conclusion, that it has density of 2,5. And since gas is <1, ice is 1 and rock is 4, it has to have a large rocky core, but mixed with plenty of ice, liquid (water, COx or methane) or gas (atmosphere).
Considering that it is in the bio-zone from the star it has been estimated that it has a surface temperature of 0-20'C.
See more on Gliese581 on Wikipedia
If we do finally a detect a habitable planet it will be frustrating for mankind to have to wait until interstellar travel becomes possible in order to visit it. That's it ever does become possible of course.
it wont be frustrating at all. if a habital planet is ever found, each and every human on Earth will demand vacations there and ALL research will be directed toward reaching it... I PROMISE YOU THAT
If history is any guide a small proportion of people will move there and then spend large amounts of time, money and effort keeping those other aliens out
lets just hope weve evolved better than that...who am i kidding, those aliens are FRAKKING SCREWED
That's the pity of it all. We take all our foibles with us and that's not good for us nor for others.
I think there's a lot of conditions to be accomplished for a planet to support life. And i think that we don't know everything of that.
I doubt we much competion for seeding the galaxy with humanity. Until we find a big sign saying "%& $^*" [eat more embryonic amphibians], the galaxy is our plumb.
What's a star for us is a sun for them.
Wanna see what an alien looks like?
Look in the mirror.
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